Method of processing crude phenols



y 1965 R. SCHUMACHER ETAL 3,184,398

METHOD QF PROCESSING CRUDE PHENOLS Filed Sept. 27, 1961 pure phenol o-cresal m/p-creaol first running: waste water residue E INVENTORS RICHARD SL'HUMAL'HER KARL FRIEDRICH LANG EMANUEL TENGLER.

DEZSOE JTEINHERZ ATTURNE Y,

steam undesired impurities.

United States Patent 2 Claims, 61. 202-46) In processing crude phenols which are obtained, for example, from coal tar or brown coal tar, difficulties have been encountered due to the fact that such crude phenols contain impurities which impart a persistently adhering foul odor to the end products, and moreover, cause discoloration of the pure distillates after a short period of time. Numerous suggestions were made previously for the removal of the above mentioned impurities. The object of these suggestions is the destruction of the impurities either by chemical actionin most cases by means of oxidizing agentsor by cleavage obtained eg. by mild hydrogenation. Such methods are expensive and require-in view of the large quantity of the materials to be treated-the use of extensive, additional apparatus.

It has also been suggested previously to remove the beforementioned impurities by subjecting the crude phenols with the addition of water to azeotropic distillation. Thus, according to US. Patent No. 1,909,546, 2000 parts of crude phenol are heated with the addition of 300900 parts of water in a distillation column. Thereby, first pyridine bases distill over and last naphthalene and sulfur-containing compounds in the form of azeoptropic mixtures with water, at temperatures below that of water. Subsequently the phenols are subjected to distillation. In this process water is added to the phenols treated in such large amounts that correspondingly large amounts have to be removed from the system and the phenols have to be separated from relatively small amounts of impurities with considerable expenditure. Thereby losses of phenols occur.

It has now been found that by proceeding in the manner described and claimed hereinafter the impurities here in question can be removed from crude phenols without the occurrence of losses of phenols in such manner that in the subsequent fractionation phenol is directely obtained a pure product which has no tendency of discoloration and has a high solidification point of e.g. 40.440.5 C.

In carrying out the process of the present invention, crude phenol is first freed from the considerable amount of water adhering thereto, and is subsequently subjected to distillation together with reflux in a dehydration column into which steam is introduced. The introduced steam acts extractively by increasing the relative volatility of the impurities present in the phenol and, therefore, it must be constantly present in the necessary concentration in said column. The steam is introduced into the sumpwhich has normally a temperature above 150 C.of a column which serves also for dehydration and is present in a non-azeotropic proportion relative to the total amount of the ascending vapors of the product. This results in column temperatures which are higher than the temperatures corresponding to the azeotropic proportion, whereby separation of the sulfur-containing compounds is favor-ably influenced.

In this process of the invention relatively small amounts of water in the form of steam, e.g. 4% by weight based on the crude phenol charge treated are sufficient in order to obtain the desired effect of complete removal of the This results in the additional advantage that smaller amounts of phenol-containing waste Patented May 18, 1965 water have to be disposed of, in comparison with the above described prior art process.

A further advantage of the present invention consists in that the steam added to the ascending vapors of the product treated in non-azeotropic proportion does not act selectively e.g. with regard to phenol, cresol and xylenol, i.e. it leaves the relative volatility thereof practically unchanged. Therefore, after separtion of the undesired impurities by the action of steam, subsequently phenol having the above mentioned high solidification points can be distilled off immediately.

If it is intended to carry out distillation continuously, in the process according to the present invention the removal by distillation of undesired impurities can be combined not only with dehydration, but also with the separation of low-boiling phenols from high-boiling phenols and from the residue. From the dehydration and residue column-which is operated under atmospheric pressurethe low-boiling phenols, e.g. phenols and cresols, are withdrawn as a side stream and, if desired, they can be purified by distilling them in the presence of a non-azeotropic amount of steam in a side column, and subsequently separatedpreferably by distillation under vacuuminto pure phenol, o-cresol and m/p-cresol.

The residue and, for example, the higher-boiling phenols extractively purified with steam, are discharged from the sump of the dehydrating column and separated, if necessary, into further components of the crude phenol, discontinuously or continuously. With regard to the yield of phenol and cresols it is favorable that the residue is already separated, because the formation of phenol pitch is thus reduced. Any residue newly formed is passed back to one of the columns connected in series, in order to discharge it together with the primary residue.

The appended drawing and the following example illustrate by way of example and without limitation a specific embodiment of and a best mode for carrying out the invention.

Example The appended drawing illustrates by way of example a system for continuous processing of crude phenol according to the invention. The crude phenol is fed at 1 into column I which is operated under atmospheric pressure and provided with a side-column Ia. Into a lower part of column I, e.g. into the sump, steam is introduced through conduit 2. The sump of the column is heated in conventional manner, e.g. in a circulation evaporator or a reboiler 3. At the head of column I a dephlegmator 4 is arranged, in which by the action of steam of low tension, partial condensation of the volatilized oils is effected, the condensed oils being thereby divided by a suitable device 5 into reflux and distillate 5 containing impurities. The residual vapors escaping from the dephlegmator are condensed in an after-condenser 6; they consist chiefly of water.

From dehydration column I e.g. phenol and cresols are passed over conduit '7 to side column Ia and are there subjected, if desired, to an after-purification. To a lower part of side column I-e.g. to one of the rectification trays or to the sump-through conduit or pipe 8-steam is fed. The phenol-cresol-rnixture--which has been purified and freed from dimethylphenols and phenol pitchis passed from the sump of side column Ia through conduit 9 to the phenol fore column 11. From the latter the m/p-cresol is withdrawn in a side-stream, while the phenol/o-cresol vapors which escape through the head of column II are separated in the connected phenol-main column III into pure phenol and o-cresol. The residue newly formed during distillation is passed through reflux-conduit 1t) and return-conduit ii to dehydration column I.

a 3 V v The material accumulating in the sump of column I is further processed in conventional manner continuously or discontinuously. The columns connected to side column Ia-i.e. columns II and III-.are preferably operated under a vacuum of 100 to 200 torrs. v v

In using in the above described procedure a crude phenol of conventional composition, in column III a phenol having an average solidification point of 40.4-40.5 C. is directly obtained. This phenol has no tendency of discoloration, is free from secondary odors and can be used without redistillation. Furthermore, due to the separation of ingredients boiling at higher temperatures than cresols together with the residue already in the dehydration column, phenol and cresols are obtained in increased yields.

The crude phenol used as starting material in the above example may consist ofthe following ingredients (after the removal of water present in the crude phenol) 2' 7 Percent. Aliphaticcarboxylic acids, pyridine bases, naphthalene, sulfur-compounds etc 1.5 Phenol(C H OH) r 39 O-Cresol I 13 m/p-Cresols 28 Higher phenols 18.5

The temperature at the head of column I maybe in the range of 110 to 160 (2., preferably about 120 C.; in the sump 185 to 215? C. and in the sump of the sidecolumn Ia about 190 C. under atmospheric pressure. The tem perature at the head of column II may be in the range of 126 to 145"C. and in the sump 139 to 158 C.;and at the head o f colu mn III-121 to 139 C. and in the sump 127 to 146 C., all temperatures being'stated for a'pres-,

sure of 100-200 torrs. In proceeding in this manner, the

following end products canbe, for example, obtained:

, sure with about phenol in azeotropic' ratio When the temperature at the head of the column reaches about 120 C., distillation is carried out under reflux and with the addition of steam, until the phenol in the firstrunnings attains the desired freezing point of at least 40 C. After, this phase. of the distillation, the pressure in the column is reduced to 100-200 torrs and pure phenol, o-cresol and 4 7 pure phenol, while the rest of the phenol is obtained by redistillation of the transitional fraction.

It will be understood from the above that this invention is' not limited to the specific materials, steps, data, conditions and other details specifically described above andcan be carried out with various modifications. Thus, the pressure of the steam introduced into the process is not limited to any specific pressure range and for processing 100 parts by weight of crude phenol (freed from water) 2 to 6 parts by weight of steam can be'used. The vacuum incolurnns II and III may be in the range of 100 to 200 torrs. a

' It will be appreciated that thernethod here claimed is an invention of high utility. The utility resides in the use of smallramounts of Water in the form of steam, in comparison with prior art processes and in the favorable yields and purity of the products obtainable by the method claimed. 7

What is claimed is:

1. A method of purifying crude phenols from impurities which impart a persistently adhering foul odor to and cause discoloration of pure phenol obtainable from crude phenol by fractional distillation, essentially consisting of subjecting crude phenols to fractional distillation in a column having a head portion, a sump, and an intermediate part between said head portion and said sump, in order to substantially distill off the water from the crude phenolgintroducing steam'into the sump in a rn/p-cresol is obtained by distillation with degrees of purity corresponding to those stated in the above example of the continuous procedure. However, in the discontin uous batch distillation, transitional fractions are also obtained, which must be'subjected to discontinuous redistillation. For example,in the discontinuous distillation of crude phenol 'about83% of the phenol are obtained'as GEORGE VD. MITCHELL, ALPHONSO ratio of 2-6 parts by weight for parts of crude phenol free from Water; partially condensing the vapors escaping through the head of the column, at about 100 C., dividing the condensate thus formed into first running distillate and substantially water free reflux; reintroducing such reflux into the head of the column and discharging purifiedphenols from said intermediate part of the column. a a i 2. A method as claimed in claim 1, in which the method is carriedout continuously; saidpurified phenols consist of a mixture of phenoland cresols, and said purified phenols are further purified by additional fractional distillation and introduction of steam, into the additional fractional distillation in a ratio of 2'6 parts by weight for 100 parts by weight of said purified phenols free from water. I 1

References Cited by the Examiner UNITED STATES PATENTS 1 1,909,546 5/33 Molinari. 2,081,884 5/37 Roberts 202-40 X 2,209, 15 O 7/40 Byrns. I 2,437,649 3/48 Milner 20246 7 2,573,244 10/51 Bogart et a1. 202-68 X 2,992,169 [7/61 Gregoryjet a1. 3,029,292 4/762 Nixon d 202- 46 NORMANVYUDKQFF, Primary Emmi/w n SULLIVAN, Examiners. 

1. A METHOD OF PURIFYING CRUDE PHENOLS FROM IMPURITIES WHICH IMPART A PERSISTENTLY ADHERING FOUL ODOR TO AND CAUSE DISCOLORATION OF PURE PHENOL OBTAINABLE FROM CRUDE PHENOL BY FRACTIONAL DISTILLATION, ESSENTIALLY CONSISTING OF SUBJECTING CRUDE PHENOLS TO FRACTIONAL DISTILLATION IN A COLUMN HAVING A HEAD PORTION, A SUMP, AND AN INTERMEDIATE PART BETWEEN SAID HEAD PORTION AND SAID SUMP, IN ORDER TO SUBSTANTIALLY DISTILL OFF THE WATER FROM THE CRUDE PHENOL; INTRODUCING STEAM INTO THE SUMP IN A RATIO OF 2-6 PARTS BY WEIGHT FOR 100 PARTS OF CRUDE PHENOL FREE FROM WATER; PARTIALLY CONDENSING THE VAPORS ESCAPING THROUGH THE HEAD OF THE COLUMN, AT ABOUT 100*C., DIVIDING THE CONDENSATE THUS FORMED INTO FIRST RUNNING DISTILLATE AND SUBSTANTIALLY WATER FREE REFLUX; REINTRODUCING SUCH REFLUX INTO THE HEAD OF THE COLUMN AND DISCHARGING PURIFIED PHENOLS FROM SAID INTERMEDIATE PART OF THE COLUMN. 